Twelve of these astronauts walked on the Moon’s surface, and six of those drove Lunar Roving Vehicles on the Moon. While three astronauts flew to the Moon twice, none of them landed on the Moon more than once. The nine Apollo missions to the Moon occurred between December 1968 and December 1972.

Apart from these 24 people who visited the Moon, no human being has gone beyond low Earth orbit. They have, therefore, been farther from the Earth than anyone else. They are also the only people to have directly viewed the far side of the Moon. The twelve who walked on the Moon are the only people ever to have set foot on an astronomical object other than the Earth.

Of the 24 astronauts who flew to the Moon, two went on to command a Skylab mission, one commanded Apollo–Soyuz, one flew as commander for approach and landing tests of the Space Shuttle, and two went on to command orbital Space Shuttle missions. A total of 24 NASA astronauts from the Apollo era flew on the Space Shuttle.

NASA's Director of Flight Crew Operations during the Gemini and Apollo programs was Donald K. "Deke" Slayton, one of the original Mercury Seven astronauts, who was medically grounded in September 1962 due to a minor cardiac arrythmia - paroxysmal atrial fibrillation. Slayton was responsible for making all Gemini and Apollo crew assignments. In March 1972, Slayton was restored to flight status, and flew on the 1975 Apollo–Soyuz Test Project mission.

The prime crew members selected for actual missions are here grouped by their NASA astronaut selection groups, and within each group in the order selected for flight.

Walter M. Schirra, Jr. – Pilot of Sigma 7 and commander of Gemini 6A, was selected to command a second CSM test flight which was canceled in late 1966, at which time he was reassigned as Grissom's backup. Twenty-one months after the Apollo 1 fire, Schirra commanded the first CSM test flight, Apollo 7.

Alan B. Shepard, Jr. – America's first man in space on Freedom 7 was originally selected to command Gemini 3, but was medically grounded for the duration of Gemini due to Ménière's disease and assisted Slayton in Flight Operations. After corrective surgery, Shepard was restored to flight status and commanded Apollo 14, the third successful Moon landing mission.

All of these astronauts had flown on Gemini, and except for White, each commanded one Gemini and one Apollo mission:

Edward H. White II - Second-seat veteran of Gemini 4 who made the United States' first walk in space, selected as Senior Pilot (second seat) on Apollo 1. White was killed with Grissom and Chaffee in the fire.

James A. McDivitt – Commander of Gemini 4, selected in late 1966 to command the first Earth orbital flight test of the Apollo Lunar Module with the CSM. This mission flew in March 1969 as Apollo 9. After his flight, McDivitt was promoted to Manager of Lunar Landing Operations, and in August 1969 was promoted to Manager of the Apollo Spacecraft Program.

Frank F. Borman II – Commander of Gemini 7, selected to command a higher Earth orbit test of the complete Apollo spacecraft. But when delays prevented the LM from being ready in time for its first flight in December 1968, Borman's mission was changed to the first lunar orbital flight of the CSM on Apollo 8.

James A. Lovell, Jr. – Second-seat veteran of Gemini 7, and commander of Gemini 12, flew as Command Module Pilot (second seat) on Apollo 8. Lovell became the first to fly a second Apollo mission as commander of Apollo 13, the third lunar landing attempt. This mission was unsuccessful, due to a Service Module electrical system failure caused by the explosion of an oxygen tank. Lovell and his crew managed to return to Earth safely.

John W. Young – Second-seat veteran of Gemini 3 and commander of Gemini 10, flew as Command Module Pilot on Apollo 10. Young later commanded the successful Apollo 16 lunar landing. He also commanded the first Space Shuttle flight, STS-1 Columbia, on April 12, 1981.

In June 1965, NASA named a group of five scientist astronauts, the first group qualified by doctorate degrees rather than test or military fighter pilot experience.[4] Geologist Dr. Harrison H. "Jack" Schmitt participated heavily in the geological training of the lunar landing astronauts, as well as assisting in the analysis of returned samples and the preparation of mission reports. In 1970, he was selected as Lunar Module Pilot for the Apollo 15 backup crew, and prime crew on Apollo 18. When program cutbacks cancelled missions 18 through 20, NASA's lunar geological community insisted on having a geologist on the Moon, so Slayton reassigned Schmitt to Apollo 17.

NASA named a group of 19 more astronauts in April 1966. None had spaceflight experience before their Apollo mission.

T. Kenneth Mattingly II – selected as prime Command Module Pilot for Apollo 13, Mattingly was exposed to German measles days before the flight and was grounded by the flight surgeon. He swapped places with his backup and flew on Apollo 16.

Charles M. Duke, Jr. – first achieved public recognition as capsule communicator during the Apollo 11 Moon landing; notable for the quote: "...we copy you on the ground. You've got a bunch of guys about to turn blue; we're breathing again. Thanks a lot."[5] Duke flew as Lunar Module Pilot on Apollo 16.

Alan Shepard was the oldest person to walk on the Moon, at age 47 years and 79 days. Charlie Duke was the youngest, at age 36 years and 201 days.

Jim Lovell and Fred Haise were scheduled to walk on the Moon during the Apollo 13 mission, but the lunar landing was aborted following a major malfunction en route to the Moon. Haise was again scheduled to walk on the Moon as commander of Apollo 19, but Apollo 18 and Apollo 19 were canceled on September 2, 1970.

Joe Engle had trained on the backup crew for Apollo 14 to explore the Moon with Cernan, but Engle was replaced by Schmitt on the primary crew for Apollo 17. Schmitt had previously been crewed with Apollo 12command module pilot Dick Gordon in anticipation of Apollo 18, but Schmitt replaced Engle on Apollo 17 after the cancellation of Apollo 18 and Apollo 19, leaving Gordon as the last Apollo astronaut to train extensively for lunar exploration without ever landing on the Moon.

Besides the twelve people who have walked on the Moon, twelve more have flown to within 0.001 lunar distance of its surface. During each of the six missions with successful lunar landings, one astronaut remained in lunar orbit while the other two landed. In addition, the three-person crews of Apollo 8 and Apollo 10 also entered lunar orbit, and the crew of Apollo 13 looped around the Moon on a free-return trajectory.

All nine manned missions to the Moon took place as part of the Apollo program over a period of just under four years, from 21 December 1968 to 19 December 1972. Of the 24 people who have flown to the Moon, 17 are still living as of August 2015.

John Young, Eugene Cernan and Jim Lovell are the only three people to have flown to the Moon twice. Young and Cernan each set foot on it during their respective second lunar missions, while Lovell is the only person to have flown to the Moon twice without landing.

During Cernan's first lunar mission on Apollo 10, he tied the present record set by Bill Anders on Apollo 8 as the youngest person to fly to the Moon. Each was 35 years and 65 days old on his launch date and 35 years and 68 days old when he entered lunar orbit. (The oldest person to fly to the Moon was Alan Shepard, who walked on its surface during the Apollo 14 mission. Shepard was 47 years and 74 days old on his launch date and 47 years and 78 days old when he entered lunar orbit.)

Because of Apollo 13's free-return trajectory, Lovell, Jack Swigert and Fred Haise flew higher above the Moon's 180° meridian (opposite Earth) than anyone else has flown (254 km/158 mi). Coincidentally, due to the Moon's distance from Earth at the time, they simultaneously set the present record for humans' greatest distance from Earth, reaching an altitude of 400,171 km (248,655 mi) above sea level at 0:21 UTC on 15 April 1970.

^This date is based on GMT. Americans alive at the time remember it as the night of July 20, 1969 (Armstrong set foot on the Moon at 10:56 p.m. Eastern Daylight Time), but the official NASA chronology was kept in GMT, so the first step was 2:56 a.m. on the 21st: [1]